The Intermediate Form of Glycine-Extended Adrenomedullin Is the Major Circulating Molecular Form in Human Plasma

• Published in: Biochemical and biophysical research communications 1998-03, Vol.244 (2), p.551-555
• Main Authors: Kitamura, Kazuo, Kato, Johji, Kawamoto, Mari, Tanaka, Miho, Chino, Naoyoshi, Kangawa, Kenji, Eto, Tanenao
• Format: Article
• Language: English
• Subjects: Adrenomedullin; Chromatography, Gel; Chromatography, High Pressure Liquid; Glycine - chemistry; Humans; Hypertension - blood; Immunochemistry; Peptides - blood; Peptides - chemistry; Peptides - immunology; Protein Processing, Post-Translational; Radioimmunoassay; Vasodilator Agents - blood; Vasodilator Agents - chemistry; Vasodilator Agents - immunology
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1998.8310

Adrenomedullin (AM), a potent vasodilator peptide, is processed from its AM precursor as glycine-extended AM (AM-gly), an intermediate form of AM. Subsequently, mature AM is converted from AM-gly by enzymatic amidation. Using two kinds of radioimmunoassay which recognize the entire AM molecule (E-AM-RIA) and C-terminal amide structure (C-AM-RIA), human plasma AM immunoreactivity was chromatographically characterized. In analyses of gel filtration and reverse phase high-performance liquid chromatography, most of the AM immunoreactivity measured by E-AM-RIA was eluted at a position identical to where mature AM and AM-gly emerged and was not recognized by C-AM-RIA. These data show that immunoreactive AM measured by E-AM-RIA is not amidated. When amidated by peptidylglycine α-amidating enzyme, the immunoreactive AM was converted to a form that can be detected by C-AM-RIA. These results indicate that most of the total AM immunoreactivity measured by E-AM-RIA represents immunoreactivity of AM-gly and that the concentration of immunoreactive mature AM in plasma is much lower than that of AM-gly. In practice, plasma concentration of AM-gly and mature AM in healthy volunteers was 2.7±0.18 fmol/ml and 0.48±0.05 fmol/ml, respectively. Furthermore, plasma concentration of AM-gly and total AM was significantly elevated in patients with hypertension compared to normotensive control. The present data indicate that most of circulating plasma AM immunoreactivity is occupied by AM-gly, an intermediate form of AM, which may reflect the process of production of AM in tissues.